[PATCH] USB: fix race in kaweth disconnect

this patch from Herbert Xu fixes a race by moving termination of
the URBs into close() exclusively.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Oliver Neukum <oliver@neukum.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>